The present invention relates to a process for producing L-lysine by fermentation.
L-lysine is one of the essential amino acids, which is widely used for various purposes such as for the preparation of medicines, additives to feedstuffs and foodstuffs and the like.
Heretofore, as processes for producing L-lysine by fermentation using a microorganism belonging to the genus Corynebacterium, there have been known processes of using strains having a nutritional requirement for various amino acids such as homoserine (U.S. Pat. No. 3,708,395), strains having a resistance to S-(2-aminoethyl)-L-cysteine (U.S. Pat. No. 3,708,395), strains having a resistance to an aspartic acid analogue or a sulfur drug (U.S. Pat. No. 4,169,763), strains having a resistance to .beta.-naphthoquinoline (FR-A-2,601,035), strains having a resistance to a purine analogue or a pyrimidine analogue (U.S. Pat. No. 4,657,860) and strains having a resistance to an iturin-related substance (EP-A-0,327,945).
As a result of various studies for obtaining strains having an improved L-lysine productivity in view of recently increased demand for L-lysine, it has been found that a strain having a resistance to iodothyronine has a remarkably improved ability to produce L-lysine.